A phase contrast magnetic resonance imaging (MRI) technique using an MRI apparatus have been widely used for noninvasive measurement of fluid flow within the human body, such as blood flow. This technique is used to acquire a reference image that does not reflect a velocity by using a gradient pulse that sets an image of a blood flow velocity to zero immediately after an R-wave of an electrocardiogram (ECG) and to acquire a velocity encoded image that have reflected a blood flow velocity by using a velocity encoding gradient. Then, a reference image and a velocity encoded image are captured. Pairs of the reference image and the velocity encoded image are continuously captured during one cycle of the ECG and until k-space is fully filled by varying the magnitude of phase encoding gradients. Then, velocity images are reconstructed from the captured images and are used to measure a blood flow velocity during one cycle of the ECG.
However, this technique has problems that only a blood flow velocity can be measured in analyzing blood flow and it is insufficient to represent a high temporal resolution and accurate blood flow.
To solve the problems, a technique for analyzing arterial and venous flow has been proposed in U.S. Pat. No. 8,837,800, etc. The proposed technique includes: selecting some of the pixels of an image in order to derive an arterial input function (AIF) and a venous output function (VOF) based on a medical image; normalizing signals in the pixels; and derive the AIF and the VOF in a blood vessel composed of pixels by using a Gaussian transform.
However, this conventional technique has problems that an AIF and a VOF cannot be accurately derived, and errors may occur. Another problem is that the technique cannot accurately identify a blood vessel from a medical image, thereby hampering analysis of blood flow in the blood vessel.